Pneumatic hammer



Oct.' 11, 1938. l O MUELLER 2,132,962

PNEUMATIC HAMMER Filed Nov. 22, 1937 nbentor v l w f/ w Y f 7 y Jn,

/ Gttornegs Patented Oct. 11, 1938 UNITED STATES PATENT OFFICE 18 Claims.

This invention relates to a pneumatic hammer and more particularly to such a device which is operated both hydraulically and pneumatically. An object of the present invention is rto provide a device of this character in which the stroke of the hammer operating means is short in length and is so arranged as to give an impact as great as that of hammer operating means having a much greater length of stroke, the blow delivered V being effected pneumatically and the compression of air for electing such blow, being secured through the operation of a hydraulically operated device.

A further object is to decrease the overall length S of the device to the minimum, this being eiected by the inclusion of a pair of pistons, one being operated hydraulically to move the other and compress the conned air to operate the second piston pneumatically. It is also an object to so arrange these pistons that the pneumatically operated piston will be moved with a rapid movement and produce a heavy blow, the compressed air being aided in effecting such movement, by vacuum created by the piston in its movement in compressing the air. In an arrangement of hydraulically operated piston and a piston operated byV compressed air, means is provided for releasably connecting the two pistons so that when the hydraulically operated piston reaches 3Q a certain point, release 0f such connection will be eiected and the pneumatically operated piston will operate through a short stroke to give a very quick and heavy hammer blow, and it is also an object to provide adjustable means for 35. eiecting this disconnection between said pistons.

A further object is to provide a hammer construction which is especially adapted for use in connection with impression dies such as dies for Y numbering or lettering, or otherwise marking metal parts of machines and devices, releasable means being provided in connection with the hammer for operating the die to eilect series numbering or lettering, that is, making impressions one after another, by automatically operating the numbering die or providing such means withan arrangement whereby the same number or mark of the die may be repeated or any desired number of blows imparted to one of the numbers of the die to give the desired impression. An embodiment of the present invention is illustrated in the accompanying drawing, wherein Figure l. is a longitudinal axial section through the hammer;

Fig. 2 is a transverse section substantially upon the line 2 2 of Fig. l, and

Fig. 3 is a side elevation of the hammerl shown as applied to a numbering die and showing a suitable valve in section for controlling the operation of the hammer, said valve being shown as electrically operated, said figure including a wir- 5 ing diagram for controlling the valve operation and a push button for controlling the supply of electric power.

In Figure l of the drawing, the hammer is shown as including a tubular body I which is 10 open at each end, the forward end being closed by a suitable head 2 which is formed with a handle 3 adapted to be grasped by the hand of the operator for manipulating the hammer. The other or lower end of the body I is closed by an 15 annular ring 4 said ring 4 and head 2 being held in place by rods 4a extending the full length of the body, said ring having an axial opening through which the socket portion 5 of a tool holding head 6 projects, the head end of the tool holder being of slightly greater diameter than the internal diameter of the bore of the body I, tl'ns bore being slightly enlarged to receive the head 6 and this increase in diameter, provides an annular shoulder 1 which is normally spaced a 2r short distance from the inner end'portion of the head 6 and thus forms a stop for the inward' movement of the said head, the tool carrying head thus having a very limited sliding movement within thecentral opening of the end ring 4 30 within which opening the socket portion li` of the head 6 is adapted to slide, piston rings 8 being provided to form a tight joint between the surface of the bore of the ring 4 and the outer surface of the socket 5. Rotation of the head 6 Within the 5 central opening of the annular closure 4, is prevented by means of one or more pins 9 carried by the ring member and slidable within an opening or openings in the head 6.

The body I is divided intermediate its ends by a partition I0, forming separate aligned cylinders, this partition being fixed within the bore in any suitable manner and this partition is formed with an extended tubular guide I I extending from the partition axially thereof toward the upper or handle end of the'body, and the bore of this guide sleeve II forms a continuation of an axial bore or opening in the partition to provide a long guide for a piston rod I 2 which is rigidly secured at one end in any suitable manner, to a secondary or pneumatically operated piston I3 slidable within the cylinder bore. The opposite end of this piston rod I2 is operatively connected to a primary hydraulically operated piston I4 by means of a ball lock indicated as a whole by the 55 numeral I so that when the two pistons are in inoperative position as shown in Fig. l, the forward end of the connecting rod l2 will be firmly locked to the piston I4 so that upon movement of the hydraulically operated piston i4, the pneumatically operated piston I3 will be moved therewith until the piston I4 reaches a point where the ball lock will be automatically released to release the piston rod and permit it and the piston I3 to move independently of the piston I4.

'Ihe piston I4 is provided with the usual piston rings I6 to make a tight joint between the eX- terior of the piston and the wall of the cylinder in which it operates and the piston rod l2 is provided with the usual split piston rings l'i along that portion of the rod which slides within the tubular bearing portion I l of the wall le, to make a tight joint between this piston rod and the wall of its bearing sleeve to prevent leakage of the liquid under pressure which is `forced into the cylinder through a passage i6 in the wall lil, from leaking around the piston rod from the-chamber I9 ahead of the piston l into the chamber 2&1 located ahead ofthe piston 63.

As shown in Fig. 3 liquid or fluid under high pressure is supplied from a suitable source not' shown, through a pipe 2l into a valve casing 22 in which is located a piston having heads 23 and 24 connected by a rigid neck portion 25 and operated longitudinally of the bore of the casing 22 by means of a rod 26 extending .from one end of the piston through one end of the casing 22 with a spring 21 sleeved upon the red between the end of the casing and the adjacent piston head 24. This piston rod 26 is connected at its outer end to the movable core oi a solenoid 2B so that upon energization of this solenoid the double piston of the control valve will be moved .against the action of the spring 21, and wires 29 lead from a source of electrical energy, not shown, and within the circuit formed by these wires is connected the solenoid 2d in the usual manner, the circuit being controlled by means of a pushbutton 30 mounted upon the handle of the hammer in convenient position to be operated by the hand of the operator in order that he may by pushing the buttonoperate the double piston of the control valve and thus 'control the supply of fluid under pressure entering the valve casing through the pipe 2l to admit this fluid pressure to the hammer cylinder at the rear of the piston I4 therein, through a pipe 3| leading from the valve casing 22 to a passage 32 formed in the handle head 2 and from this passage through a pipe 33 and a nipple 34 screwed into the side wall of the cylinder in communication with the passage i6 in the wall I0. i

Therefore by manipulating the push button 30, the solenoid 28 will be energized and pull the doubleV piston of the control valve to a position with the piston head 24 located beyond the endof the pipe 3| opening into the cylinder of the valve, this movement of the valve piston being against the action of the spring 21 but unopposed by the trapping of the air within the cylinder in advance of the head 24, as the cylinder or casing 22 is provided with an opening 35 to permit the air to escape so that as soon as the head 24 passes the end oi the pipe 3l, the uid under pressure will enter the cylinder through the pipe 2i and pass out through the pipe 3l into the cylinder of the hammer through the passage 'I8 at the rearof the piston I4 and force this piston forwardly or toward the handle head of the hammer. In the `valve casing 22 there is also an opening 36 for the free entrance and exit of air beyond the head 25. When the piston of the control valve is moved to uncover the end of the pipe 3|, it will also have uncovered the end of a pipe 31 leading from the casing 22 to a passage 38 formed in the head 2 and opening at` its inner end into the endof the chamber I9. Therefore upon movement of the primary piston I4 by the admission of liquid under pressure, the chamber I9 ahead of this piston will be open through the passage 38 and pipe 31 to the atmosphere, through the casing 22. Upon deenergization of the solenoid 28, the spring 21 will operate to return the double piston to normal position as shown in Fig. 3 and in that position liquid under pressure will enter the cylinder into the space between the heads 23 and 24 and then pass out through the pipe 31 into the chamber I9 ahead of the piston I4, causing this piston to be moved back to its original position as shown in Fig. 1 with the ball lock I5 again operative to lock the end of the connecting rod I2 to the piston I4.

The ball lock I5 for detachably connecting the end of the rod I2 to the piston I4 con- -sists of a series of balls 39 mounted within radial openings in the head onV the end of the rod and this end of the rod is provided with a longitudinal bore 40 to receive a plug 4I slidable in this bo-re with a spring 42 interposed between the inner end of the plug and the end of the bore for moving the plug outwardly. The outer end of the plug 4I is reduced in diameter as at 43 so that when the plug is moved inwardly within the bore, the balls 39 mayY drop inwardly and away from seats 44 formed in the inner side or wall of the axial bore of the piston I4 and thus disconnect the connecting rod I 2 from said piston I4. Upon outward movement of the plug 4I, the balls will ride up upon the annular inclined shoulder 45 formed by the reducing of the outer end of the plug, and will be forced radially outward within the lateral bores in which they are located and be seated within the seats 44 in the piston I4, thus locking the end of the rod I2 to said piston so that the piston and rod will move together when liquid under pressure is forced into the cylinder for the piston I4 and move said piston forwardly into the chamber I9. This movement carries the secondary piston I3 forwardly because ofthe connection of the rod I2 thereto and therefore the air trapped within the chamber will be compressed. At the same time this forward movement of the secondary piston enlarges the chamber at the rear of the piston, creating a partial vacuum in this chamber 46, which vacuum will move the tool carrying head 6 inwardly to the limit of its movement defined by thershoulder 1, and air is prevented from entering this chamber 46 by means of a check valve 41 of any suitable construction but which valve will open and allow any air confined within the chamber 46 to escape upon movement of the DS ton I3 toward the head 6.

The end of the piston I3which is opposed to the head 6, is provided with a hardened disk 48 to strike the headwhen the piston is moved forwardly and then released, the air compressed in the chamber 20 moving the piston quickly and with a heavy impact. The release of the piston rod l2 from the piston I4, is eiected when the piston I4 is moved by fluid pressure into the chamber I9, 4bringing the plug 4l into contact with an abutjects into the chamber I9 in axial alinement with the plug. n When the piston I4 moves far enough to bring theplug 4I into contact with the abutment s crew, the plug is moved 'endwise within its bore against the action of the spring 42 and as the enlargedl end of the plug passes from beneath the balls 38, these balls drop inwardly down the inclined portion 45 of the 'plug and are thus disengagedffrom 'the seat '44 for these balls in the inner wall of the piston-I4, thus releasing the piston rod- IZ so that the air under compression in the chamber` 20 will quickly force the piston I3 into contact with the tool carrying head 6 with a sharprhammer blow, the force ofthe rcompressed air,'being supplemented by the partial vacuum in the chamber 46. The abutment screw 49 is adjustable longitudinally so that it will project to a greater or lesser extent into the chamber I9 and thus lessen or increase the extent of the stroke of the piston I3. To prevent the plug 4I from being resisted in its inward movement against the action of the spring 42 by air trapped behind the plug, this p1ug` is` lformed with a lon` gitudinal air duct or passage V5I] affording communication'between the chamber I9 and the end of the bore in which the plug reciprocates, and thisfabutment screw 49is held in its adjusted position bymeans of a lock nut 5I.

After a time; a portion VVof the'air in the chamber ZllmayV leak bythe piston I3 to such an extent thatn in the normal or inactive position of said piston, the air'pressure in said chamber will be below atmospheric, and therefore va check valve -52-is provided to control a passage 53 in the partition I0, which passage opens into the forward end o-f the chamber 20, this check valve being arranged to permit air to enter the charnber Z' when pressurev is below atmospheric so that air in said chamber will never drop below atmospheric pressure and the volume will always be suilicient torc'reate maximum compression 'upon forward movement'of the piston.`

UAs 'shown in Fig. 3, a numbering or other similar rotating die block `54 is applied to the hammer to make' 'marks or impressions .upon the w'ork, this rotative" die block being provided with a" series of individual die membersv or ysteel type 55k projectingv from its periphery and this die block is'rriountedwithin a yoke 56 having a stem to project into the socket 5, of theY tool head E. lThe die' block'thus receives the' full force of the hammer .blows upon the head 6 to make impressions on the work by each of thedie members`55 vand this die block `54 is automatically rotated'to present the die members 55 successively to thev work or to hold the die block against rotation and subject one of the die members toW a series'of hammerblows, Aas desired. The automatic adjustment or positioning ofthe die block 54 Yis accomplished y'by means of a plunger 51 in the form of a piston slidable within a bore formed'lon'gitudinally of the wallk of the cylinder I and which bore 58 is in communication at one end with the chamber 20 through a passage 59. T1119 Vplunger 51 is provided with a rod 60 extending froml one end thereof through a bearing in the head 4 of the cylinder and at its outer end is connected in yany vsuitable* manner with an 0pe`rating'arm` 6I`connected `to the die block' 54 in such a manner that longitudinal movement of the rod'willeifect a step by step rotation of the die block.

Compressed air in the chamber 20 entering the bore 5l through thepassage 59 will force the plunger 51 longitudinally against action of a coiled spring 62 sleeved upon the rod 60 between the head of the plunger and the end of the cylinder 58 in which the plunger operates. Therefore upon'longitudinal movement of the piston I3 the air compressed thereby in the chamber 20 will operate the plunger 51 and rotate the die block v54V one step, bringing the next die number into operative position. Therefore upon each stroke of-the piston I3 a succeeding number on the die block will be presented to the work automatically.

If, however, it is desired to hold the die block in the position to which it is last adjusted, a latch device is provided for holding the plunger 51 against return movement after it has been moved longitudinally by air pressure in the chamber 20 and therefore any desired number of blows may be succeedingly delivered to impress this particular number 55 upon the work and by moving the work and die block relatively any single number may therefore be repeated any desired number of times. If, however, it is desired to number in numerical succession, the die block will be rotated one number at each stroke of the piston I3 by holding the latch means out of engagement with the plunger 51.

.This latch mechanism'comprises a latch 63 mounted within a chamber in a lateral lug on the wall of the plunger cylinder 58 to be held in contact with the plunger by means of a lever 64 pivoted intermediate its ends and pivotally connected atxone end to the latch 63, the latch being forced inwardly by means of a spring 65 interposedbetween the handle end `of the lever 64 and the adjacent side of the cylinder so that upon longitudinal movement of the plunger 51, and portion 66 of the plunger which is reduced in diameter, this portion forming a groove in the plunger to receive the latch 63 and thus lock the plunger against longitudinal movement. When, however, it is desired to rotate the die block 54 to another position, the operator will press inwardly upon the handle endiof the lever 64 and thus withdraw thelatch 63 from the groove 66 and permitthe Vspring 62 to move the plunger back to normal position to be operated upon the next stroke of the piston I3 by air pressure against f the lend of the plunger entering through the passage 59 from the chamber 20.

*Obviously the hammer may be employed to operate any tool other than the die block 54 said tool having a shank portion to t within the socket 5 `of the head 6 of the'hammer, and it is also 'obvious that any suitable form of control valve 22 may be employed and operated electrically as described or otherwise, as found desirable; Electrical control of the hammer is, however, found preferable as a control button 30 may bejlocated in a very convenient position for operation by the hand of the operator While holding the hammer by means of the handle 3. Otherichanges in the construction, arrangement and combination of parts as shown, may also be made withinthescope of the appended claims and I Vdo not therefore wish to limit myself to the particular construction shown.

Y Having thus fully described my invention what I claim is:

l. A device of the character described including pistons and cylinders, means for operating oneof said pistons by fluid under pressure, means connecting said pistons for moving another of said pistons by the movement of said piston moved by fluid pressure and adapted yto 4compress a fluid, and means ,ii'or effecting a-disconnection between said pistons to allow onev of said pistons to be operated by fluid compression independentiy of the other pistonn;

2. A device` for the purpose",described inciuding a pair ofalined cylinders and pistons, means for moving one iof said pistons by fluid under pressure, means for detachably; connecting said pistons to move one the pistons and effect fluid compression, by the movement of the otherpis-` ton, and means for effecting disconnection between said pistons to allow one to be operated by fluid under compression independently of the other piston.

3. A device of the character describedincluding a pair of Yalined cylinders, a pistonvin each cylinder, a connecting rod for connecting said, pistons, and means for 'detachably connecting said connecting rod to one of vsaid pistons to permitone piston to move independently of the other.

4. A device of' the character described including alined pistons and cylinders, a wall separating said cylinders, apistonrod connected to one oi said pistonsr and'extending through said wall, means for detachably connecting. the end of said rod to said piston beyond. said wall, and means for moving said piston ,beyond` said wall and vto elect a disconnection of said rod from said piston when said piston has moved a certain distance and has moved the other piston through the connection of said rod ,theretoy to compress uid ahead of said last namedzpiston, said last named piston being moved by such compression when so released, to strike ahammer blow. y

5. A device of theV character described'includ-'- ing a pair of cylinders in axial. alined relation and separated by a xed wall, a powerpiston in one of said cylinders, a compression piston in the 'other .of said cylinders, detachable means connecting said pistons, and means for eiecting a disconnection between-said pistons upon movement of said power piston to effect a compression lof fluid ahead of said compression piston and permit said compression piston to be moved byviiuid compression under compression and the. other of said'pistons being a compression piston, a piston ro'd fixed to said compression piston, means vforoperativelyr connectingjsaid. rod to saidpower piston, and means for operating said connecting means 'to disconnect'said pistons and permit said compression piston to be move-:i by ,fluid compression in dependentlyof said power piston.

-7. A device ofthe character described including a pair of axially alined cylindersfa wall'se'parating the adjacent ends of said cylinders, a' power piston in one of said cylinders, a compression pistonin the other of said cylinders, a toolcarrying head in the outer end cisaid cylinder for said compression piston, means vfor operativelyv connecting said pistons to move together in one -direction of movement, andv means for disconnecting said connecting means to permit said compression pistcn lto be moved' by fluid compression-and by partial vacuum in said cylinder formed by forward movement of said compression cylinder therein.. y

8. A pneumaticallyr operated hammer including a pair of alined cylinders, a piston in each cylinder, one of said pistons being moved longitudinally vby fluid under Vcompression' within-fits cylinder, 'a tool carrying head in the outer end of saidcylinder, a connectingrod secured at one end said last Vnamed piston andextending through an axial bore inthe other piston, means for detachably connecting the f orward end of said rod tofsaid piston having said bore, and means extending into the cylinder for said piston having said vbore to engage, and operate'said connecting means to disconnect said pistons after forward movementA of -bothpistons. Y

,-9. AA devicey of the character described including a cylinder having a head with an axial bore, toolcarrying head having a limited sliding movementl within the end of said cylinder and having a'zsocket portion slidable within said bore of said `h ead, a. piston in said cylinder adapted to eiect fluid compression upon movement therein awayfrom .said head, a second cylinder in axial alinement with l said rst named cylinder and separatediwherefrom by a transverse wall, the outer end of said second cylinder being closed by a head, a piston in said second cylinder, means for introducing iluid under pressure behind said second pistonin said second cyiinder, a connecting rod securedto said first named piston and extendinginto an axial bore of said second piston, means for detachably connecting the forward end ofsaid connecting rod with said second piston, and operating means extending through the head of said second cylinder to engage and operate said disconnecting means and effect a disconnection of said rod fromsaid second piston upon movement of said second piston toward said head of said cylinder to bring said disconnecting means into engagement with said operating means.

10. A device of the ,character described including a pair of axially alined cylinders and means for separating said cylinders interposed between their adjacent ends, a power piston in one of said cylinders adapted to be movedendwise within said cylinder by uid under pressure, compression piston in the other of said cylinders, a piston vrod connecting said pistons to move together in the same direction, means for disconnecting the forward; end of said rod from said power piston after movement of said pistons to eiect uid compressionahead of said compression piston, and a tool carrynghead in the outer end of said cylinder for-saidcompression piston and having a limited longitudinal movement in said cylinder and adapted to be impactedwith a hammer blow by said compression piston .upon release of said connesting rod from said power piston.

11. A hydraulically and pneumatically operatedjfhammer including a hydraulically operated piston-,andr a `pneumatically operated piston in axial alineinent with said hydraulically operated piston, a4 cylinder for each of said pistons, means connected to said pneumatically operated piston and extending into an axial bore of said hydraulically operated piston, releasab-ie means for connecting said means tosaid hydraulically operated pistonafter-movement of said pistons in the same directionand after compression of iluid ahead of said vcompression piston, to permit said compressionvr piston to move independently of said hydraulicaiiy operated piston and strike a quick hammer blow at the outer end of its cylinder.

A device of the'character described including a pair of -axially alined cylinders, a transverse wall -separating said-cylinders at their adjacent ends and provided with axial longitudinal bearing, a piston operated by fluid under pressure in one of said cylinders, a compression piston in thev other of said cylinders, a connecting rod congnecting said pistons to cause them to move together inthe same direction,Vv said rod slidable within said bearing upon said Wall dividing said cylinders, releasableconnecting means for connecting the forward end of said -rod with said power piston, means forgoperating said connecting means extending into the chamber inthe cylinder for said power piston, andv a tool carrying head in the 'gouter end of said cylinder for said compression piston and having a limited longitudinal movement therein and adapted to be struck a hammer blow by said compression piston upon its release from said power piston by said releasable connecting means.

13. A device of the character described comprising a pair of cylinders in axial alinement and separated from each other at their adjacent ends by a transverse wall, a power piston in one of said cylinders operated by fluid under compression entering through a passage in said wall at the rear end of said power piston, a compression piston in the other of said cylinders, a rod secured at one end to said compression piston and extending through an axial bore in said power piston, locking means for locking the forward end of said rod to said power piston, an adjustable member extending through the head of said cylinder for said power piston and adapted to engage and operate said locking means to disconnect said pisto'ns when said power piston has moved forwardly and through such movement has moved said compression piston to compress fluid within its cylinder and to create a partial vacuum rearwardly of said piston upon such movement, said compression piston being moved by fluid compressed in advance thereof by movement of said power piston and when released therefrom, said power stroke of said compression piston being aided by partial vacuum created rearwardly of said piston by its forward movement, and a tool carrying head within the outer end of the compression piston cylinder adapted to be struck a hammer blow by said compression piston.

14. VA device of the character described including a pair of axially alined cylinders and pistons therein, means for introducing fluid under compression at the rear of one of said pistons, an operative connection between said pistons to eiect simultaneous forward movement of said pistons within their cylinders, said connection including a connecting rod secured at one end to one of said pistons, means for connecting the other of said pistons to the other end of said rod, and a ball lock for detachably connecting the end of said rod to said piston, said ball lock comprising a series of balls mounted within radial openings in a head of said rod and adapted to seat within a seat in the inner surface of a bore of saidpiston, said lock also including a plug movable within a longitudinal bore in the end of said rodf and formed with an annular shoulder adapted to permit said balls to drop inwardly when said plug is moved endwise, and means for engaging and moving said plug longitudinally when said piston has moved longitudinally within the chamber of its cylinder and has effected a similar movement of said other piston.

15. A device of the character described includ- Ving a pair of axially alined cylinders, a transverse wall separating said cylinders at their adjacent ends and formed with a passage opening into the forward one of said cylinders, means for forcing fluid under pressure through said passage into said cylinder, a power piston in said cylinder adapted to be moved by said fluid under pressure,

`a compression piston in the other of said cylinders, a connecting rod secured at one end to said .compression piston and extending axially through said powerv piston, means at the forward end lof said rod for detachably connecting said rodvto said power piston to cause said pistons to move jtogether. in thesame direction and releasable t .permit said'. compression piston to move under compression independently of saidpower piston, means for effecting a disconnection between said rod and said power piston upon forward movement of said pistons, a tool carrying head having a limited longitudinal movement within the outer end of said cylinder for said compression piston and adapted to be struck a hammer blow by said piston upon its release from said power piston, said head and said outer end of said compression piston forming a limited chamber therebetween for creating a partial vacuum within said chamber upon forward movement of said compression piston, and a check valve in operative communication with said vacuum chamber to prevent flow of air into said chamber and to permit the escape of air therefrom.

16. A hammer structure comprising a pair of axially alined cylinders, a transverse wall separating said cylinders at their adjacent ends and formed with an axial bearing sleeve, a power piston within the forward of said cylinders and formed with an axial longitudinal bore to receive said bearing sleeve, a compression piston Within the other of said cylinders, a connecting rod secured at one end to said compression piston and extending through said bearing sleeve, said rod being formed with an axial bore extending inwardly from its forward end and having a head at said end formed with radial openings to receive balls, said power piston being formed in the wall of its bore to provide a seat for said balls which balls when so seated lock the forward end of said rod to said power piston, a plug within the bore of said rod and formed with an annular shoulder to permit inward movement of said balls upon inward movement of said plug, a spring interposed between the inner end of said bore and the inner end of said plug, a head closing the forward end of said cylinder for said power piston, an abutment screw mounted within a screwthreaded opening in said head and projecting into the chamber ahead of said powerpiston to engage the end of said plug and move the same longitudinally to release said balls and disconnect said rod from said power piston, said wall dividing the adjacent ends of said cylinders being formed with a passage and said head being formed with passages, one Vto receive a conduit for conducting fiuid under pressure to said passage in said wall and the other of said passages opening into the forward end of said cylinder for said power piston, a source of supply under pressure, and valvular means for controlling the flow of such fluid into and through said passages in said head.

17. A hammer device including a pair vof alined cylinders, a power piston in one of said cylinders, a compression piston in the other of said cylinders, means for operatively and detachably connecting said pistons to move together in one direction, means for releasing said means to permit said compression piston to move independently of said power piston under the influence of fluid pressure ahead of said pressure piston, a tool carrying head in the outer end'of said cylinder for said compression piston adapted to be struck hammer blows by said piston and having a socket to receive a tool, a tool mounted within said 'socket and having a plurality of impression mem- Abers-carried by a movable head, and means op- -erated by fluid under compression from the chamfsckei; of said tool carrying head and provided with a rotatable die having a series of peripheral impression members, and means for rotating said Yrotatable die, said means for rotating said die being operated by a plunger mounted Within a bore in the wall of a cylinder, which bore is in communication at, one end with the compression chamber ahead of said compression piston.

OTTO MUELLER. 

